import java.util.Scanner;

public class demo006 {
    public static void main(String[] args){
        Scanner scan=new Scanner(System.in);
        System.out.println("请输入成绩");
        int a=scan.nextInt();
        if(a<60)
        {
            System.out.println("c");
        }
        if(a>=60&&a<80)
        {
            System.out.println("b");
        }
        if(a>=81&&a<=100){
            System.out.println("a");
        }
    }
}
